FAS and colorectal cancer: Second, wildtype HCT116 cells or HT29 cells with high expression of PIR are resistant to FAS mAb‐ or CD8+ T cells‐induced cell death, in contrast, moderate downregulation of PIR even though being not sufficient to initiate apoptosis can dramatically sensitize HCT116 colorectal cancer cells to either FAS mAb‐ or CD8+ T cells‐induced cell death.